This invention relates to improvement in so-called "child-resistant" closures which are becoming more and more necessary in view of the emphasis being placed upon the dangers inherent in the presence in the household of containers of poisonous and harmful substances such as bleaches, detergents, alcohol, anti-freeze fluid, drain openers and the like.
Many efforts have been made to provide child-resistant closures. The most successful of these closures have been those which have met the following criteria:
1. The closure and its container must have some cooperating means which require disengagement by an action different from merely unscrewing the cap and this action must require either a separate manipulation in a direction incomprehensible to a small child or the closure must be of such size that a small child cannot successfully grasp it in his hands or between his teeth.
2. The secondary manipulation to enable opening of the closure or removal of the cap must be such that an older child or an adult readily can grasp the significance and perform the necessary manipulation.
3. Preferably, the cap should be of such nature, for example a screw-on type, which can be placed upon the container by conventional capping machinery thus to eliminate the requirement for the purchase of special machinery by producers and fillers of the containers.
4. Preferably, the cap should consist of one piece to reduce the cost by requiring only a single mold in the cap manufacturing plant and to eliminate the labor necessary for the assembly of two-piece caps.
5. Preferably, the neck finish on the container with which the cap is to be used should have a standard thread so that ordinary caps can be placed upon such containers if desirable or to replace the "child-resistant" cap in case that it becomes lost.
6. Preferably, the cap should have threads or other retaining means which will enable it to be used on other containers should that event occur.
One of the principal problems which has been encountered in endeavoring to design child-resistant closures or caps and containers, has been to take into account two variations in the manufacture of both parts. The first of these is the necessary manufacturing tolerances in order that the cooperating means such as the mating threads on the cap and container neck will be functional. The second of these problems arises from the fact that these tolerances may cumulate adversely and either make it impossible for the child-resistant features to be properly aligned when the cap is closed or else to allow the cap to move well beyond its child-resistant position so that the small child can rotate the cap in a retrograde direction up to the child-resistant stop and, many times, cause the entire container to leak its dangerous substance.
Many screw-type caps and container necks have been designed which comprise a radially or downwardly extending tab on the cap itself and an abutment on the neck of the container or on a shoulder of the container adjacent the base of the neck so that, after the cap is screwed onto the container in liquid sealing position, the tab on the cap lies ahead of the abutment on the container so that the child is not able to turn the cap in a retrograde direction beyond the engagement of the tab with the abutment. However, because of the two types of tolerances mentioned above, this frequently results in the necessity for designing the threads and the relative angular positions of the tab on the cap and the abutment on the bottle or container so that when the cap is placed on the container by an automatic capping machine, it will be turned beyond its child-resistant position. In addition, when an older child or an adult restores the cap to the container after first opening, it frequently is turned beyond its child-resistant position.
Because of the pitch of the so-called "standard" threads, which usually are about 6 to the inch, each ten degrees of angular rotation of the cap relative to the bottle neck may result in as much as a variation of 0.005 inch vertically and, if, for example, the cap is turned 40 or 50.degree. beyond the position where the child-resistant elements engage, and the child then turns it back to child-resistant position, the cap may be able to move up and down a substantial distance relative to the neck, and a leaker is almost certain to result.
It is, therefore, the principal object of the instant invention to provide a child-resistant closure for dangerous liquids and the like in which the two cooperating elements of the child-resistant feature automatically are positioned on the cap and container in their child-resistant juxtaposition regardless of whether or not the tolerances mentioned above cumulate in either direction. As a result, when a cap and neck finish embodying the invention are assembled by rotating the cap onto the container neck, the container is sealed against the escape of liquid and will continue to be so sealed every time that the cap is returned onto the neck to the child-resistant position.
It is yet another object of the instant invention to provide a threaded cap for the threaded neck of a container, the cap carrying with it both elements of its child-resistant cooperating means comprising a tab affixed permanently to the cap itself and an abutment which rotates with the cap until the cap is seated on the container in liquid sealing position whereupon the portion of the cap carrying the abutment element of the child-resistant means is permanently fixed to the container by, for examples, ultrasonic or heat sealing or adhesive.
It is yet another object of the instant invention to provide a child-resistant cap which automatically will properly align its cooperating means which render the cap child-resistant regardless of whether or not the tolerances accumulate and which also will be tamper-indicating thus to prevent the cap from being removed off of the container without that fact becoming apparent.